Dissolved Organics Filtration/Removal

Hi Folks,

I'm interested in knowing which products, if any, you all use to remove dissolved organics from aquarium water. I'm not referring to the likes of Stress Zyme, Waste Control, etc. Instead, I'm talking about materials that are added to the filter - be that internal or external. One example is granulated active carbon (GAC). There are several commercial products such as Seachem Purigen.

Dissolved organic carbon (DOC) can cause a lot of problems. As heterotrophic bacteria break it down, it can lower the oxygen level in the tank water. It can also contribute to oily films on the water surface. And it can form a film at the entrance to CO2 drop checkers, which leads to incorrect readings.

I am currently using Seachem Renew as it's supposedly better than Seachem Purigen for planted tanks. But, I'm not convinced that Renew is effective. Let me qualify that. I get an oily film on the water surface, which I would not expect to be there while using Renew. I will contact Seachem about this later today.

GAC, or just 'activated carbon' has a multitude of uses. It is often used to remove medications from the water following a period of treatment of sick fish, for example. It can also be used to remove tannins if the water has taken on a brown colouration from leaves such as Catappa.

So, does anyone have any suggestions for products that I could try?

Thanks in advance.

JPC

I don't, and have never, used any of these products, even when I kept live plants. I'm happy with the brown-stained colouration of the water from the catappa leaves. I use activated carbon in the quarantine tank filter after I've used it as a hospital tank involving medication but that's all.

Hi @fcmf

Many thanks for your reply.

I also like the brown tannins from the Catappa leaves. And it's the tannins + other humics that are therapeutic for the fish, as I understand it. But it's the oily film that bugs me as it can interfere with gas exchange (CO2/O2) at the water surface.

JPC

A little surface agitation fromt he filter outflow or an airstone should be able to deal with the film without having to resot to adding chwmicals to the tank. Or are you going after DOC specifically? I've never given it much cause for concern, but I tend not to worry too much for what I don't understand. Is it something I should be researching?

Hi @Matt

Surface agitation does not always help to disperse or remove the film. I often find it to be completely ineffective. I have tried a lot of surface agitation in this instance - so much that people were queuing up with their surfboards to ride the waves! I don't see the addition of all filtration media as adding chemicals. Activated carbon and similar products act as molecular sieves by adsorbing organic molecules, which are larger than inorganic ions, for example. Their mode of action is different from ion exchange resins.

Yes, in this instance, I am only concerned with DOC.

JPC